The invention relates to a temperature sensor, in particular a high temperature sensor, comprising a substrate, at least two terminal contacts and at least one resistive structure, wherein the terminal contacts and at least one of the resistive structures are disposed on a first side of the substrate, and wherein at least one resistive structure is electrically contacted by the terminal contacts.
The invention also relates to a method for producing such a temperature sensor, in which at least one resistive structure is applied to a first side of a substrate, and to a high temperature sensor comprising such a temperature sensor.
A temperature sensor made of metal of the platinum group is known from WO 92/15101 A1, comprising a platinum resistive layer applied to a ceramic substrate and a passivation layer applied thereon.
U.S. Pat. No. 5,202,665 A discloses a method for producing a temperature sensor, wherein a platinum layer is applied to a substrate using the thick-film technique. Platinum powder is mixed with oxides and binders for this purpose and applied by way of screen printing.
Moreover, an electrical measuring resistor structure for resistance thermometers and a method for producing such an electrical measuring resistor structure are known from U.S. Pat. No. 4,050,052 A or DE 25 27 739 C3.
JP 57114830 A discloses a temperature sensor, in which a measuring electrode for determining the temperature on a substrate is surrounded by a second electrode so as to determine the humidity by a resistance measurement of the surface of the substrate between the electrodes.
A similar construction is proposed in EP 0 437 325 A2, in which the surface resistance or the internal resistance of the substrate is determined with the aid of two additional electrodes, which are disposed next to a resistive layer on the substrate or on the other side of the substrate.
To produce such a temperature-dependent resistor as a temperature sensor, the Pt resistive layer is applied as a thick film in meander-shaped form onto a substrate having a surface made of electrically insulating material, wherein the outer surface of the resistive layer is covered by a layer made of electrically insulating material, which serves as a passivation layer. The problem with such sensors is that metallic ions can migrate into the resistive layer and damage, or even destroy, the same, in particular at high temperatures. This causes the properties of the temperature sensor to be changed.
A method for producing a temperature-dependent resistor comprising platinum as a temperature sensor is known from EP 0 543 413 A1, wherein an electrode is applied at a distance from the resistive layer. This is intended to prevent ion migration to the resistive layer caused by current conduction. The electrode is electrically conductively connected to the resistive layer for this purpose.
EP 0 327 535 B1 discloses a temperature sensor having a thin-film platinum resistor as a measuring element. A temperature measuring resistor made of platinum is disposed on a surface of an electrically insulating substrate, wherein the resistance element is covered by a dielectric protective layer, which is preferably made of silicon dioxide and has a thickness ranging from 200 to 400 nm. Moreover, a diffusion barrier layer is provided as the topcoat, which is applied by the deposition of titanium in an oxygen atmosphere so as to form titanium oxide. This barrier layer has a thickness ranging from 600 to 1200 nm. While the diffusion barrier layer allows access of oxygen to the dielectric layer, and thereby partially prevents an attack of freed metal ions diffused out of the glass layer on the platinum layer, under extreme ambient conditions an attack on the platinum layer may nonetheless take place, so that they physical behavior thereof as a temperature sensing element is impaired.
According to EP 0 973 020 A1, such temperature sensors may be fitted with a sacrificial cathode and withstand temperatures of up to 1100° C. This technique protects the measuring shunt from chemical or mechanical attacks. However, it must always be assure in this sensor that the cathode is properly electrical connected, because a mixup of the electrical connections results in destruction of the sensor. In addition, the sensor is subject to drift at temperatures starting at 700° C.
A temperature sensor having a Pt resistance film is known from DE 10 2007 046 900 A1, the layer being covered by a thin film made of aluminum oxide. A cover is glued onto the ceramic film covering the resistance film. A glass ceramic which is doped with metal and which is electrically conductively connected to one of the terminal surfaces of the temperature sensor forms a sacrificial cathode to protect the resistance layer from harmful influences of metal cations, and to thereby reduce the aging process of the temperature sensor or prevent the temperature sensor from being destroyed. The influence of the power supply connection and polarity of the housing in which the sensor is installed may cause the sensor to drift.
The drawback of all these temperature sensors is that the temperature sensors have a complex design comprising several layers, some of which are complex. Due to the complex design, the production requires many work steps, whereby the costs for production of such a temperature sensor are high.
Another considerable drawback is that the polarity must be observed during installation or use of the temperature sensor because otherwise the temperature measurement may worsen or the temperature sensor may be unfit for use, or the temperature sensor may even be destroyed the first time it is operated.